<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }
        .bigbox{
            width: 500px;
            height: 500px;
            border: 10px solid gray;
            margin: 100px auto;
            /* 弹性盒子 */
            display: flex;
        }
        .bigbox div{
            width: 50px;
            height: 50px;
            border: 2px dashed red;
        }
    </style>
</head>
<body>
    <div class="bigbox">
        <div>1</div>
        <div>2</div>
        <div>3</div>
        <div>4</div>
        <div>5</div>
    </div>
</body>
</html>